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Virtual Colonoscopy - Topic Overview

How is it done?

Virtual colonoscopy is usually done in the radiology department at a hospital or medical center. The test is most often done by a doctor who specializes in performing and interpreting diagnostic imaging tests (radiologist). The doctor may also have an assistant.

You will need to take off most of your clothes. You will be given a gown to wear during the test.

First, you will be asked to lie on your back on the table of the CT or MRI machine. A thin tube is inserted into the rectum through the anus. For CT, air or carbon dioxide gas will be pumped through the tube. (There may be some discomfort as the gas expands your colon.) For MRI, a contrast liquid will be given through the tube into the colon. This helps the doctor see all parts of your colon.

The table will slide into the CT or MRI machine so pictures of your colon can be taken. You may be asked to hold your breath when pictures are taken. This can help prevent blurry pictures. Then the procedure will be repeated while you lie face down.

The test usually takes about 10 minutes.

How does a virtual colonoscopy differ from a regular colonoscopy?

Virtual colonoscopy has advantages and disadvantages compared to a regular colonoscopy.


  • Virtual colonoscopy is less invasive, safer, and takes less time than a regular colonoscopy.
  • A thin tube to insert air into the colon is placed in the rectum rather than a long flexible tube that is moved up your colon.
  • No medicine to relax or sedate you is needed, so you will be able to drive yourself home and resume normal activities.
  • Virtual colonoscopy can show the inside of a colon that is narrow due to inflammation or an abnormal growth.


  • Virtual colonoscopy may not show polyps smaller than 10 mm (0.4 in.).
  • Virtual colonoscopy is not covered by all health insurance plans. Check with your insurance plan before having the test.
  • If a polyp is found, regular colonoscopy will be needed to confirm the diagnosis and remove the polyp so it can be looked at under a microscope.
  • This is a newer test and isn't as widely available as regular colonoscopy.
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